Running a filter on an instance

Hi, I want to write a filter that runs once on the instance. I know about the “Process font with arguments” method, but does something similar exist for the instance on which the filter is called?

Thanks!

What exactly are you trying to do?

I want to run a duplexer filter as an export filter.

Duplexer;wght:150;ital:0

That gets the metrics from the corresponding axis location and I want to apply them to all layers.